With increasing development of industries, various robots have been developed and widely used in people's daily life and industrial applications. Generally, robot manipulator is an important component of the robot and may be equipped with a tool on the end-effector thereof for performing required tasks. For example, the tool may be a welding tool, a drilling tool, a gripping tool, a milling tool, or a cutting tool. The tool secured to the end-effector of the robot manipulator has a defined tip point, called the Tool Center Point (hereinafter referred to as TCP). When the tool is mounted on the end-effector of the robot manipulator, the precise displacement variations of the TCP of the tool relative to the end-effector of the robot manipulator need to be acquired and defined in advance. Namely, the size of the tool must be measured when the tool is mounted to the robot manipulator. When the robot manipulator equipped with the tool performs the required task, the operated paths and positions of the robot can be automatically calibrated according to the acquired displacement variations for allowing the tool to be operated at the correct operated paths and positions.
At present, for facilitating to calibrate the TCP of the tool, a tool calibration apparatus is employed. The conventional tool calibration apparatus includes a frame body and a plurality of infrared sensors. When the tool is mounted on the end-effector of the robot manipulator, a tool calibration process is performed. Firstly, the tool is moved toward the tool calibration apparatus and a modeling and teaching process of the tool is performed. Namely, the robot manipulator drives the tool to move within the space defined by the frame of the tool calibration apparatus, and the tool calibration apparatus performs a teaching process and sets up a pattern of moving the tool according to the movement of the TCP. Consequently, when one tool is replaced with another one with similar type, the tool calibration apparatus can compare the displacement variations between the tools and allow the robot manipulator to compensate for the tool inaccuracy so as to achieve the tool calibration process.
However, the conventional tool calibration apparatus equipped with infrared sensors is extremely expensive. In addition, when one tool mounted to the robot manipulator is replaced with another one with similar type, the displacement variations of the TCP of the tool relative to the end effector of the robot manipulator can be acquired by the conventional tool calibration apparatus with infrared sensors. However, when one tool mounted to the robot manipulator is replaced with another one with different type, the displacement variations of the TCP of the tool relative to the end effector of the robot manipulator can't be acquired accurately by the conventional tool calibration apparatus with infrared sensors. Consequently, the accuracy of the tool calibration performed by the conventional tool calibration apparatus is degraded. In addition, the misalignment of the tool may shut down the entire production line and waste material, time and cost.
Therefore, there is a need of providing a tool calibration apparatus of a robot manipulator to obviate the drawbacks encountered from the prior arts.